Having grown up in Baltimore City and moved to Baltimore county, I can say that Baltimore fans do have a bit of a persecution complex. It's not only sports. Baltimore is always in the shadows of Washington, DC, New York, and to some degree Philadelphia. Look at weather events. There are always reports out of Washington and New York during east coast blizzards, Baltimore is just assumed to be wrapped up in them. The rivalry with Pittsburgh stems from the Browns moving here and being in the same division, but goes deeper than that. Pittsburgh was never much more than an afterthought in Baltimore before 1970. But the Pirates beat the Orioles in the 1971 world series, and then broke Oriole fans hearts by coming from a 3-1 deficit in 1979 during the Orioles magical season. The Steelers were never any rival to the Colts until the mid 70's. The Colts with Bert Jones came from a last place finish to win their division and went to Pittsburgh and played the Steelers tough, but eventually lost. The next year they got a somewhat beatup Steelers team at home, only to get blown out from the word go. The Ravens have never beaten the Steelers in three tries during the playoffs. You mention Alleghaney county. All of the Maryland counties from Washington west are more Pittsburgh fans than Baltimore fans. I found that out when I went into an Oakland, Md sports bar only to find pictures of Terry Bradshaw, Jack Lambert, Mario Lemioux, and Willie Stargell plastered on the wall. I asked the bartender if this was a "Pittsburgh" bar and he looked at me funny. He explained that Pittsburgh is much closer than Baltimore and has more in common with the mountain terrain of western Maryland. It remains that way to this day. Baltimore will always have to fight the stigma of being an east coast city that is stuck between Washington DC, and New York.
Hey, but the Steelers gave Baltimore Johnny Unitas.